Known in the present state of the art is an electrosurgical instrument which is comprised of two electrodes, i.e., a small-area active electrode serving as the working electrode proper, and a larger-area passive electrode ( cf. the paper entitled "Application of biactive bipolar electrodes in electrosurgery" by S. M. Shamraevsky et al. in the journal "Vestnik khirurgii imeni I. I. Grekova", No. 1, pp. 66-67 issued in 1971) (in Russian).
It is common practice that the passive electrode is bandaged to the lateral surface of the left thigh, or put under the patient's back, whereas the active electrode is used to carry out the surgical procedure involved. In this case the current field lines are dispersed in the tissues, thus concentrating in low-resistance areas and passing by those featuring poor electric conductance.
Use of the aforesaid instrument involves no clear-cut borderline between coagulated and sound tissue and may inflict damage to some organs and tissues located distantly of the place of application of the active electrode. In addition, orientation of the coagulation process as for direction and depth is impeded, and burns are likely to occur at the place of the passive electrode application.
One more prior-art electrosurgical instrument is known to comprise a body and coaxial electrodes of which the outer passive one is rigidly held in the body, while the central active electrode is traversable with respect to the outer electrode (cf. U.S. Pat. No. 4,043,342, Class A 61 B 17/32 published in 1977).
The instrument enables the current field lines to be concentrated at the active electrode situated in close proximity to the passive electrode, whereby the working zone is reduced drastically which makes practicable to carry out single-point coagulation or fine dissection of a tissue, e.g., in layer-by-layer excision of the gastric wall.
However, when surgery is performed by the aforesaid heretofore-known instrument the latter is liable to get out of order rather quickly due to carbon deposition on the active electrode, which thus interferes with further surgical procedure. Therefore the instrument is to be cleaned of carbon deposit repeatedly in the course of surgery, which is carried out manually and involves withdrawal of the instrument from the working zone, thus prolonging the operating time and complicates the surgeon's job.